ABSTRACT
Mg-Si thin films with various elemental compositions ranging from 0≤x≤1 in MgxSi(1-x) were obtained via combinatorial magnetron sputter deposition of Si and Mg in order to improve the electrochemical lithiation/delithiation process of pure Si by embedding Si in an active Mg-Si matrix. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy methods were used to investigate the morphology, stoichiometry, and structure of the different thin film samples. Constant current charge/discharge cycling revealed significant electrochemical changes depending on the Mg content in comparison to the pure Si active material improving the capacity retention to 96% over 400 cycles.
ABSTRACT
Tin is able to lithiate and delithiate reversibly with a high theoretical specific capacity, which makes it a promising candidate to supersede graphite as the state-of-the-art negative electrode material in lithium ion battery technology. Nevertheless, it still suffers from poor cycling stability and high irreversible capacities. In this contribution, we show the synthesis of three different nano-sized core/shell-type particles with crystalline tin cores and different amorphous surface shells consisting of SnOx and organic polymers. The spherical size and the surface shell can be tailored by adjusting the synthesis temperature and the polymer reagents in the synthesis, respectively. We determine the influence of the surface modifications with respect to the electrochemical performance and characterize the morphology, structure, and thermal properties of the nano-sized tin particles by means of high-resolution transmission electron microscopy, x-ray diffraction, and thermogravimetric analysis. The electrochemical performance is investigated by constant current charge/discharge cycling as well as cyclic voltammetry.
